Surface Morphology Of Electrode Research Articles

The Behaviors of Interfacial Nanobubbles on Flat or Rough Electrode Surfaces in Electrochemistry.

The existence of interfacial nanobubbles on electrode surfaces is thought to block the active area, leading to a considerable decrease in the energy conversion efficiency. Gaining insight into how bubbles form on electrodes will be beneficial for designing effective electrochemical cells and enhancing the electrolytic efficiency. In this article, molecular dynamics (MD) simulations are employed to make a systematic comparison of behaviors of interfacial nanobubbles on both flat and rough electrode surfaces in electrochemistry. On a flat electrode surface, bubble nucleation can be categorized into single-site and multisite nucleation, influenced by the electrode sizes and electrolytic rates. The various rates of gas production result in three different scenarios for single-site nucleation: "growth-growth," "growth-shrinking," and "growth-stabilization" behaviors. On a rough one, bubbles are pinned at an early stage. Either through cooperative release or self-release, the bubbles continue to grow until the influx and outflux gas of the bubble reach an equilibrium. In addition, the evolutionary mechanism of interface nanobubbles was discussed on a rough nanoelectrode surface. Based on the dynamic equilibrium mechanism, a theoretical relationship between contact angle and base diameter of equilibrium interfacial nanobubbles was developed. The theoretical model can qualitatively describe the simulation observation of how bubble's shape depends on the electrode surface morphology.

Binder-Coated Carbon Cloth Electrodes for All-Vanadium Redox Flow Batteries

Vanadium redox flow batteries (VRFBs) are a promising solution for integrating intermittent renewable energy sources into the existing power grid. However, enhancing the electrochemical performance of VRFBs is critical for their widespread adoption in grid-scale energy storage. This study investigates the impact of adding a porous binder to a carbon-cloth electrode, with a focus on optimizing thermal activation conditions. The electrochemical performance of the binder-coated electrodes compared to uncoated electrodes is evaluated through electrochemical impedance spectroscopy, polarization curve measurements, and charge-discharge cycling. The surface morphology and structural integrity of the binder-coated electrodes at each activation stage are examined using various material characterization techniques to assess the effects of thermal activation. The results are benchmarked against the experiments using non-coated electrodes to determine the performance improvements offered by the binder coating. Notably, the study reveals that binder-coated electrodes exhibit significantly lower resistance and improved efficiency compared to their uncoated counterparts, with optimal activation conditions enhancing performance metrics crucial for VRFB applications. These findings provide valuable insights for further optimizing electrode design and activation strategies, advancing the development of more efficient VRFB systems for large-scale energy storage.

Economical iron-based catalyst electrode for highly stable catalytic industrial-scale overall seawater splitting

The development of economical and stable catalyst electrodes for industrial-scale seawater splitting is one of the current challenges in hydrogen production. The economical transition metals possess high electrical conductivity and offer the potential for designing electrodes with high intrinsic activity through appropriate modifications, thus holding promising applications in industrial contexts. Herein, a durable and economical self-supported bifunctional electrode (Fe@Ni) with high efficiency and large area is successfully constructed by one step in-situ deposition of iron on the porous structure of nickel foam (NF) via mild (298 K) electroplating method. Transition metals like iron and nickel offer high electrical conductivity and can be properly modified to achieve electrodes with high intrinsic activity. Due to the in-situ growth of cost-effective iron on the NF surface, the electrode surface morphology and electronic structure are reconstructed, which significantly improves the electrochemical activity surface area and electron transfer capability of the electrode. The hydrogen/oxygen evolution reaction (HER/OER) in simulated seawater (1 M KOH + 0.5 M NaCl) require only 129 mV and 323 mV overpotentials to achieve a current density of 100 mA cm−2. Overall seawater splitting (OWS) achieves 10 mA cm−2 at a low voltage of 1.49 V and with a faradaic efficiency of nearly 100%. More importantly, the bifunctional electrodes remain stable at industrial-level current density (1.0 A cm−2) for more than 50 days. More attractively, this work realizes the universal construction of large-area electrode for multiple metals (e.g., Fe, Cu, Al, etc.) with mild and simple process, which provides a new strategy for the current research of energy and materials.

Sensitivity Improvement of Electrochemical Virus Detection through Morphology Control of CNT Electrodes

The global pandemic of influenza virus (IFV) and Covid-19 has created a strong need for the technology to measure viruses quickly and sensitively. Currently, PCR-based detection technology is used to accurately detect these viruses, however they lack immediacy as it takes several days for the viruses to grow to detectable amounts. A complementary method that allows immediate detection is an antigen testing that uses complementary substances (aptamers and antibodies) that specifically bind to target virus. Among them, electrochemical detection via cyclic voltammetry is being researched as a method that can measure target virus in solutions with high sensitivity and high speed. Since these utilize chemical reactions on the electrode surface, the material and surface morphology of the electrode are important factors that govern sensitivity. Previous research has reported that highly sensitive and robust virus testing can be performed by using carbon nanotube (CNT) films, which are chemically stable and have a large surface area, as chemical electrodes. However, the effect of the surface morphology of CNT films such as structures and defects has not been sufficiently studied.In this study, we attempted to increase the sensitivity of electrochemical virus testing by controlling the surface morphology of CNT films and increasing the amount of aptamer adsorption. The morphology of the CNT film was controlled through heat and non-heat laser processing by using 532 nm nano-second and/or pico-second pulsed lasers. The fabricated morphology was evaluated by SEM and polarized Raman spectroscopy. In addition to measuring the amount of aptamer adsorption for each morphology using ultraviolet spectroscopy, we also evaluated the detection sensitivity of IFV when using the CNT films as an electrochemical electrode. As a result, we achieved the high sensitivity and reliability IFV detection with fg/ml of the limit of detection. In the presentation, we will introduce the developed CNT morphology control technology and discuss the relationship between morphology and aptamer adsorption amount. Figure 1

Electrochamical CO2 Reduction Characteristics with Various Copper-Based Alloy Plating Electrodes

Climate change caused by global warming has led to disasters in many countries around the world. The Sustainable Development Goals (SDGs) call for "taking specific measures against climate change." The time has come for humanity to think concretely about ways to suppress the increase in greenhouse gases, which ate thought to be the cause of global warming, and to actually implement them. Among the known greenhouse gases, carbon dioxide (CO2) accounts for about 75% and is recognized as an important target. Various efforts have already been made to reduce CO2 emissions. On the other hand, in order to reduce the amount of CO2 emitted into the atmosphere, technologies for geological storage and conversion of CO2 are indispensable. CO2 becomes a resource if it can be converted into useful industrial resources such as carbon monoxide, formic acid, or hydrocarbons in processes that utilize surplus or renewable energy. Many electrochemical reduction techniques have been studied for CO2 conversion, and Dr. Yoshio Hori has conducted a comprehensive study of electrochemical reduction of CO2 using metal electrocatalysts1). It has been clarified that the products are different depending on the metal species, and studies are underway to change the surface morphology and crystal planes of metal electrodes and to combine multiple metals in metal electrocatalysts. These previous studies were to reveal that the adsorption strength of CO2 and electrodes is based on the metal type of the electrode, and that changing the electrode metal changes the path, efficiency, and products of the electrochemical reduction reaction.The object of this research is to take a bird's-eye view of the characteristics of CO2 electrochemical reduction using copper-based alloy plating electrodes, which we have been development. Among metal electrodes, copper, which can produce hydrocarbons, has been the most widely studied for CO2 electrochemical reduction. When a copper-cobalt electrode is prepared by alloy plating, the ratio of the hydrocarbons, methane and ethylene, changes depending on the mixing ratio of cobalt. In this copper-cobalt electrode, cobalt exists as a substituted solid solution in the copper crystal structure, and it is considered that the generation efficiency of ethylene is reduced and that of methane is increased due to the inhibition of C-C bonding.When copper-tin electrodes are prepared by alloy plating, unlike cobalt, a solid solution or an intermetallic compound may be formed depending on the ratio of copper and tin. Since the atomic radii of tin atoms are quite different from those of copper atoms, tin atoms do not exist only in substituted solid solution as in the case of cobalt, but their crystal structure changes. The reduction properties of CO2 electrochemical reduction at a copper-tin electrode were changed. Copper produces hydrocarbons and tin produces formic acid as the main products of CO2 electrochemical reduction, while carbon monoxide is produced as the main product at a copper/tin ratio of 87:13.Computational chemistry studies predict that the formation of hydrocarbons by copper is via the two-electron reduction product carbon monoxide. The presence of tin near the copper atoms is considered to weaken the adsorption between copper and carbon monoxide. The modeling of the adsorption and the attempt to elucidate the cause by computational science revealed that the tin atoms are weakly bonded to the reaction intermediates and act only as the active sites for the formation of formic acid. It was found that the copper atom weakens the bond with carbon monoxide due to the presence of the tin atom next to the copper atom, and that it decreases the amount of adsorption of hydrogen and carbon monoxide. It is reported that the amount of carbon monoxide adsorbed on copper atoms is important for the formation of hydrocarbons, which is stabilized by the formation of hydrogen bonds with CHO*, the reaction intermediate to hydrocarbons. These results suggest that the adsorbed carbon monoxide is destabilized, and carbon monoxide is desorbed from the copper atom, resulting in an increase in carbon monoxide as a product.

Operando Characterization of CO2 Reduction Interfaces by Electrochemical Atomic Force Microscopy

The electrode-electrolyte interface is perhaps the most important interface of an electrochemical device. At this interface, the electrochemical reactions of interest occur, and the local microenvironment (e.g. pH, reactant concentrations, water activity) can differ significantly from bulk electrolyte conditions due to double layer formation, migration, mass transport effects, catalyst restructuring, and more. In addition, common electrode materials such as polycrystalline metal foils and nanoparticle catalyst layers are heterogeneous with regions of differing activity, making the interface vary across the surface of the electrode both spatially and temporally. Understanding the electrode-electrolyte interface, its local microenvironment, and the evolution of the heterogeneous electrode surface is crucial to the development of high performing electrochemical devices. However, traditional electrochemical methods average current and potential measurements across the electrode surface. Thus, combining electrochemistry with advanced in situ and operando is necessary for a holistic view of the electrode-electrolyte interface.Scanning probe techniques are well-suited for operando studies of electrode-electrolyte interfaces due to their compatibility with liquid environments and suitable spatial (µm to nm scale) and temporal (minutes to seconds) resolutions. One popular operando technique for the study of electrode-electrolyte interfaces is electrochemical atomic force microscopy (EC-AFM). EC-AFM measures the interaction forces between a sharp physical probe and sample surface to map the surface topography. These measurements can also extract information about the sample’s mechanical properties by generating force-distance curves across the surface. EC-AFM measurements are readily performed in a three-electrode cell under potential bias, thereby allowing spatially and temporally resolved imaging of the electrode-electrolyte interface in operando.Here, we applied EC-AFM to two studies of the electrode-electrolyte interface during the electrochemical CO2 reduction reaction (CO2RR). First, we present EC-AFM measurements of a common degradation mode for CO2RR electrolyzers: salt precipitation. CO2RR produces OH-, which accumulates at the electrode-electrode interface and causes the local pH to shift more alkaline. However, this alkaline environment also promotes the formation and precipitation of (bi)carbonate salts by the reaction of OH- and CO2. Herein, we conducted EC-AFM measurements on a Ag electrode in calcium-containing bicarbonate electrolytes. CO2RR was catalyzed at the Ag surface to cause a local pH shift at the electrode surface and result in the formation of CaCO3 crystallites on the electrode surface. Through EC-AFM measurements, we investigated the effect of applied current and bulk electrolyte pH on this deleterious mineralization process.Second, we studied the interactions between polyethylenimine (PEI) and a Ag catalyst. PEI is a polymer that can capture CO2 from the atmosphere by forming a carbamate. Recent work has shown that CO2 bound in PEI can be directly converted to CO without an intermediate CO2 release step. However, very little information is known about the interaction of the polymer with the electrode surface during CO2RR. We studied the morphology and mechanical properties of a Ag electrode surface in PEI-containing electrolytes as a function of applied potential and electrolyte composition for the conversion of CO2 to CO. Both variables significantly affected the mechanical properties (i.e. modulus) of the electrode surface, suggesting polymer chain reorganization at the interface due to interactions with electrolyte species and charged electrode surfaces. Overall, these examples demonstrate that EC-AFM is a powerful operando technique for building fundamental understanding of the electrode-electrolyte interface.

Catalytic Properties of FeCoNi Alloy Electrode for Alkaline Water Electrolysis Prepared by Anodizing

1.Introduction Alkaline water splitting, a low-cost and simple hydrogen production method, has been attracting attention to the realization of a sustainable society. However, the overpotential of the oxygen evolution reaction (OER) on the anode is high and the hydrogen production efficiency is low. Catalysts containing Fe, Co, and Ni are expected to be promising candidates for electrodes materials [1]. Recently, we succeeded in fabricating FeNi and FeNiCo alloy electrodes covered with a porous metal fluoride film by anodizing, which exhibited better OER activity and durability than OER catalysts [2]. We reported that the metal fluoride films synthesized by anodizing in fluoride-containing organic electrolytes converted to metal oxyhydroxide during OER in KOH aqueous solution. However, the physical properties of the films and electrode characteristics, which are the factors responsible for the high OER activity of this electrode, remain unclear.In this study, various commercial FeNiCo and FeNi alloys (Kovar: Fe-17 mass% Co-29 mass% Ni, 42-Invar: Fe-42 mass% Ni, 45-Permalloy: Fe-45 mass% Ni, 78-Permalloy: Fe-78 mass% Ni) were anodized to fabricate highly active OER electrodes and applied to in-situ Raman spectroscopic characterization to understand the activation mechanism of the anodized alloy electrodes.2.Experimental Commercial FeCoNi and FeNi alloys were used for electrode preparation. The electrolytes used for anodizing were ethylene glycol containing 0.54 M NH4F and 2.5 M H2O for Kovar, 45-Permalloy, and 42-Invar, and ethylene glycol containing 0.08 M NH4F and 0.02 M H2O for 78-Permalloy. The anodizing process was performed at 10 V for 60 min at 293 K in an ethylene glycol-based electrolyte, and platinum was used as the counter electrode. The surface morphology and composition of the OER electrodes were measured using field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. In-situ Raman measurements were conducted using laboratory-made cells. The measurement was performed using a three-electrode system with a platinum counter electrode and an Hg/HgO electrode as the reference electrode under a flow of 1 M KOH aqueous solution at 24.0 mL min-1. In-situ Raman spectra were measured under potentiostatic conditions every 0.2 V from 1.13 V vs. RHE.3.Results and discussion【morphology and compositional characterization】 The surface morphology of the films was highly dependent on the composition of the FeCoNi and FeNi alloys. A uniform and smooth film with an average thickness of 200 nm was observed in the anodized 78-Permalloy electrode, and non-uniform films with an average thickness of 1 µm were observed in the anodized 45-Permalloy and 42-Invar electrodes. The anodized Kovar electrode exhibited a non-uniform and wide crack film with an average thickness of 2.5 µm. The cationic composition of the films was also dependent on the composition of the commercial FeCoNi and FeNi alloys. The anodized 78-Permalloy electrode showed the lowest Fe content in the film.【Raman measurement】 The ex-situ Raman measurements revealed the presence of mixed phases of spinel oxide and metal oxyhydroxide for all electrodes after OER, indicating that the metal fluoride films were completely converted to metal oxide and metal oxyhydroxide. Then, in-situ Raman measurements were conducted under the controlled potential in 1 M KOH aqueous solution. The peak intensity of spinel oxides decreased and that of metal oxyhydroxides increased with increasing applied potential. Because the spinel oxide peaks disappeared and those of metal oxyhydroxide were only observed at the OER onset potential for all electrodes, the in-situ measurements revealed that metal oxyhydroxide is an active phase for OER in the electrolysis system. Interestingly, when the electrode potential was returned to negative, the film structure reverted to the mixed phases of spinel oxide and metal oxyhydroxide. Therefore, we confirmed that the anodized electrodes possess structural reversibility. However, since no trend was observed in the correlation between structural change behaviors and the order of OER activities of the electrodes, other factors would also contribute to OER activities in addition to the formation of the metal-oxyhydroxide structure.

Visualizing Solid Electrolyte Interphase Formation in Carbon Nanotube-Based Lithium-Ion Batteries: A Comparative in-Operando Electrochemical Atomic Force Microscopy Study

Reducing the impact of the climate crisis is this centuries greatest challenge and requires a global effort. Renewable energy sources are the key to decarbonising our energy systems. Lithium-ion batteries (LIBs) have played a key part in tackling the climate crisis and their continued development is imperative to further reducing the impact. More than ever, researchers are incorporating additives and components into battery electrode materials to enhance their electrochemical behaviour, such as their cyclability, conductivity and capacity retention. Carbon nanostructures as additives have been envisioned to offer solutions to problems associated with volumetric fluctuations as well as low conductivities in some next-generation LIBs.Carbon nanotubes (CNTs) have been researched since 1991 and are essentially rolled up single or multiple sheets of graphene to produce single-walled CNTs or multi-walled CNTs respectively. The incorporation of CNTs into LIBs enhances conductivity and improves mechanical properties, enabling better tolerance to volume expansion. Despite these benefits, CNTs contribute to an initial irreversible capacity charge loss in the first cycle. Unlike the capacity loss seen in graphitic anodes, the high surface area of CNTs leads to increased electrolyte decomposition, forming the solid electrolyte interphase (SEI). This is essential for stable, long-term cycling. Given the limited understanding of SEI formation and growth in conventional LIBs, the introduction of CNTs further complicates this process.In this work, in-operando electrochemical atomic force microscopy (EC-AFM) is employed to investigate the evolution of the electrode surface morphology. It can provide real-time information about the changing topography of the electrode surface as the electrochemical environment changes. Thus, processes leading to SEI formation on CNT and CNT:graphite electrodes will be visualised. A comparison is made with graphite:CNT electrodes, revealing a rapid SEI formation on the CNT electrode and a slower one on the graphite:CNT electrode. This demonstrates that the graphite:CNT ratio significantly influences SEI formation and, consequently, electrochemical performance. EC-AFM proves powerful in real-time probing of the effects of changing potential on an electrode surface, highlighting where SEI first nucleates and subsequently grows. This technique facilitates a direct correlation of electrochemical analysis with topographical images, offering invaluable insights into how initial electrochemical processes impact the electrode surface at micro- and nano-scales, applicable across various battery chemistries.

Au‐Free Ti/Al/Ni/TiN Ohmic Contact to AlGaN/GaN Heterostructure: Ti/Al Thicknesses at an Optimized Ratio

Although a few studies report that tuning Ti/Al thicknesses at a fixed ratio can further improve the Ohmic contact to AlGaN/GaN heterostructure, systematic physical mechanisms have not been reported. In this work, after determining the optimal Ti/Al ratio of 1/4, two metal stacks with varying Ti/Al thicknesses and fixed Ni/TiN thicknesses are deposited to investigate how tuning Ti/Al thicknesses at an optimized ratio enhances the Ohmic contact performance. At the optimal annealing condition (950 °C, 45 s) of samples with Ti/Al thicknesses of 20/80 nm, samples with Ti/Al thicknesses of 35/140 nm exhibit a reduction of 48% in contact resistance and 70% in specific contact resistivity (ρc). By correlating the results from ρc–T measurements, time‐of‐flight secondary ion mass spectrometry, and high‐resolution X‐ray diffraction, it has been determined that this method effectively enables N‐vacancies doping into the heterostructure, thereby increasing the carrier concentration and reducing both the height and width of the interfacial potential barrier, achieving a more efficient carrier transport. By avoiding the use of Au with high solubility and ductility, this approach significantly improves contact performance without adversely affecting the electrode surface morphology, demonstrating good adaptability for optimizing Au‐free Ohmic contacts.

Exploring Platinum Thin Films as Electrodes for High‐Temperature and ‐Pressure Electrochemical Studies in Aqueous Systems

ABSTRACTThis work reports a methodology for the fabrication of Pt thin‐film electrodes for electrochemical studies in hydrothermal systems. The research process was meticulous, with particular attention paid to the multilayer Ti/Pt/Ti/Al2O3 film structure and annealing conditions that are expected to impact the morphology of the films, surface composition and electrochemical response. The findings of this study are significant, as they provide valuable insights into the behaviour of Pt thin‐film electrodes in various media and conditions. Two different approaches were adopted for the preparation of the electrodes: in one case, the Ti/Pt/Ti/Al2O3 films deposited on sapphire wafers were exposed to rapid thermal annealing at 900°C under argon for 5 min, followed by argon ion milling to etch the final electrode pattern (Pt‐RA(900)), while in the other case, uncapped Pt films were annealed, after etching, in a tubular oven under argon at specific temperatures between 200°C and 900°C (Pt‐TO). Rapid annealing at 900°C on capped films resulted in the formation of a Pt3Ti intermetallic alloy with remarkable mechanical and chemical stability even after 10 h of immersion in deionised water, acid (0.1 M H2SO4) and alkaline media (0.1 M KOH) conditions at temperatures up to 150°C, despite the dissolution of the Al2O3 top layer at 150°C and long immersion times (> 10 h). In the case of uncapped Pt films, diffusion and oxidation of Ti through the Pt film at high temperature resulted in the formation of TiO2 on the surface of Pt. The results were confirmed by using a comprehensive suite of ex‐situ characterisation techniques to follow changes in the Pt electrode surface morphology and composition before and after immersion in H2O, 0.1 M H2SO4 and 0.1 M KOH solutions under argon. Ex‐situ electrochemical characterisation studies were also conducted to correlate the changes in the electrode surface properties, including the electrochemical surface area, with different annealing conditions and after various hydrothermal treatments in neutral, alkaline and acidic media.

Correlation of residual stress on piezoresistive properties of boron-doped diamond films

To investigate the influence of residual stress on the piezoresistive behavior of boron-doped diamond (BDD) films, BDD films with varying doping concentrations were synthesized using a hot-filament chemical vapor deposition (HFCVD) system on silicon and diamond substrates. The relationship between the surface morphology, structural composition, resistivity, and piezoresistive properties of BDD electrodes was examined, along with an in-depth analysis of the impact of boron doping level on these properties. The microstructure and bonding state of the BDD films were characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and Raman spectroscopy. The piezoresistive properties of the BDD films were evaluated employing a cantilever beam bending method. Our findings demonstrate that the level of boron doping not only affects resistivity but also directly influences residual stress in BDD films, both factors having an impact on their piezoresistive properties. Despite significantly larger grain sizes observed in BDD films grown on diamond substrates compared to those grown on silicon substrates at identical boron doping concentrations, they exhibit consistent variations in residual stress and gauge factor (GF) values. With increasing doping levels, the absolute residual stress decreases initially before increasing again; moreover, at 2000 ppm doping level, it transitions from compressive to tensile stress. The GF value is closely associated with both the magnitude and type of residual stress. By utilizing a doping concentration of 2000 ppm for growth on diamond substrates, we achieved a peak GF value of 257 for BDD films which highlights their promising potential for pressure sensor applications.

Substrate and potential-driven surface morphology of bifunctional Ni-Fe electrode for efficient alkaline water electrolysis

Nickel-iron (Ni-Fe) alloy electrodes are synthesized using chronoamperometry. The influence of substrate type (copper, stainless steel, and nickel) and deposition potential on the structural, morphological, and electrocatalytic characteristics are systematically investigated. X-ray diffraction (XRD) analysis revealed the formation of a face-centered cubic (FCC) Ni-Fe alloy. Electrodeposition at higher potential (−1.45 V) forms well-defined nanoflakes, whereas electrodeposition at lower potential (−1.00 V) results aggregated Ni-Fe particles. The Ni-Fe alloy electrodes having well-defined nanoflakes demonstrated superior electrocatalytic performance, exhibiting a overpotential of −168 mV vs. RHE for the hydrogen evolution reaction (HER) and 236 mV vs. RHE for the oxygen evolution reaction (OER), at current density of 10 mA/cm2. The enhanced electrocatalytic activity of the nanoflakes based Ni-Fe alloy is attributed due to their larger catalytic surface area, porous morphology and higher Fe concentration. The Ni-Fe alloy electrodes displayed bifunctional electrocatalytic behavior, making them highly suitable for both HER and OER processes.

Voltammetric Sensor Based on Titania Nanoparticles Synthesized with Aloe vera Extract for the Quantification of Dithiophosphates in Industrial and Environmental Samples

In this work, TiO2 spherical nanoparticles with a mean diameter of 10.08 nm (SD = 4.54 nm) were synthesized using Aloe vera extract. Rutile, brookite, and anatase crystalline phases were identified. The surface morphology of a carbon paste electrode does not change in the presence of nanoparticles; however, the surface chemical composition does. The voltammetric response to dicresyl dithiophosphate was higher when the electrode was modified with TiO2 nanoparticles. After an electrochemical response study from pH 1.0 to 12.0, pH 7.0 was selected for the electroanalysis. The electroactive area of the modified sensor was 0.036 cm2, while it was 0.026 cm2 for the bare electrode. The oxidation process showed mixed adsorption-diffusion control. The charge transfer resistance of the modified sensor (530.1 Ω, SD = 4.08 Ω) was much lower than that of the bare electrode (4298 Ω, SD = 8.53 Ω). The linear quantitative range by square wave voltammetry was from 5 to 150 μmol/L, with a limit of detection of 1.89 μmol/L and a limit of quantification of 6.26 μmol/L under optimal pulse parameters of 50 Hz frequency, 1 mV step potential, and 25 mV pulse amplitude. The sensor response was repeatable and reproducible over 30 days. The results on real flotation and synthetically contaminated soil samples were statistically equivalent to those obtained by UV-vis spectrophotometry. A dithiocarbamate showed an interfering effect on the sensor response to dithiophosphate.

Influence of Bi3+ Doping on Electrochemical Properties of Ti/Sb-SnO2/PbO2 Electrode for Zinc Electrowinning.

Bi3+ doped Ti/Sb-SnO2/PbO2 electrode materials were fabricated by electrodeposition to improve their electrochemical performance in zinc electrowinning. The surface morphology, chemical composition, and hydrophilicity of the as-prepared electrodes were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and contact angle. An electrochemical measurement and an accelerated lifetime experiment were also conducted to investigate the electrocatalytic performance and stability of the electrodes. The results show that the Bi3+ modification electrode has an important effect on the coating morphology, the crystal structure, the surface hydrophilicity, the electrocatalytic activity, and the stability. The electrode prepared from the solution containing 2 mmol·L-1 Bi(NO3)3 (marked as the Ti/Sb-SnO2/2Bi-PbO2 electrode) exhibits the best hydrophilicity performance (θ = 21.6°) and the longest service life (1196 h). During the electrochemical characterization analysis, the Ti/Sb-SnO2/2Bi-PbO2 electrode showed the highest oxygen evolution activity, which can be attributed to it having the highest electroactive surface (qT* = 21.20 C·cm-2) and the best charge-transfer efficiency. The DFT calculation demonstrated that the doping of Bi3+ leads to a decrease in the OER reaction barrier and an increase in the DOS of the electrode, which further enhances the catalytic activity and the conductivity of the electrode. Moreover, the simulated zinc electrowinning experiment demonstrated that the Ti/Sb-SnO2/2Bi-PbO2 electrode consumes less energy than other electrodes. Therefore, it is expected that the Bi3+ modified electrode will become a very promising electrode material for zinc electrowinning in the future.

Balancing current density and electrolyte flow for improved zinc-air battery cyclability

Zinc-air batteries (ZABs), known for their high energy density and environmental friendliness, are emerging as promising solutions for sustainable energy storage. However, the irregular deposition of zinc on electrodes hinders the widespread utilization of rechargeable ZABs due to limited durability and stability. This study investigates the role of electrolyte flow in enhancing zinc electrodeposition and overall performance in zinc-air flow batteries (ZAFBs) at high current densities. We explore the interplay between current density, flow rate, and their influence on electrode surface morphology and the removal of the passivating zinc oxide layer to improve battery efficiency and lifespan. Using advanced in-situ synchrotron radiation x-ray tomography, we found that incorporating flowing electrolyte at specific current densities results in rounded dendrite tips, thinner and more uniform deposition layers, and improved zinc adhesion. Imaging and electrochemical analyses further reveal that flowing electrolyte enhances zinc morphology, reduces charge transfer resistance, diminishes passivation, and lowers galvanostatic charge/discharge polarization across various current densities, thereby improving battery cycling performance. Notably, the impact of flowing electrolyte is more pronounced at a moderate current density of 50 mA/cm2 compared to lower or higher currents. Our findings underscore the importance of electrolyte flow and current density management in developing high-performance ZAFBs, providing valuable insights for their future commercialization.

Nitrate reduction on bimetallic (Pd0.09Sn0.91) electrodes: Effects of calcination temperature, electrode support, and quenching

The effects of fabrication process, namely, calcination temperature, electrode support, and quenching, on electrochemical nitrate reduction were investigated, exemplified by Pd0.09Sn0.91 electrode. The electrode was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and cyclic voltammetry. Results showed that electrode surface morphology, crystalline formation, and chemical composition, which were influenced by the electrode fabrication process, controlled nitrogen selectivity and nitrate reduction reactivity. The Pd0.09Sn0.91/SS electrodes were calcined at different temperatures (from 100 to 700 °C) for 3 h in air and the results showed that high calcination temperature rendered electrode oxidized, and decreased nitrogen selectivity and nitrate reduction capability. Electrode supports affected nitrate reduction following the order of Ni ≈SS > G > Ti. Quenching electrode in ice water decreased nitrate reduction capability. Porous surface with small oxygen content, less degree of metal oxidation (i.e., higher fraction of Pd0 and Sn0), and Sn crystals favored nitrogen selectivity and nitrate removal.

Mechanism of overscreening breakdown by molecular-scale electrode surface morphology in asymmetric ionic liquids

The interfacial nature of the electric double layer (EDL) assumes that electrode surface morphology significantly impacts the EDL properties. Since molecular-scale roughness modifies the structure of EDL, it is expected to disturb the overscreening effect and alter differential capacitance (DC). In this paper, we present a model that describes EDL near atomically rough electrodes with account for short-range electrostatic correlations. We provide numerical and analytical solutions for the analysis of conditions for the overscreening breakdown and DC shift estimation. Our findings reveal that electrode surface structure leads to DC decrease and can both break or enhance overscreening depending on the relation of surface roughness to electrostatic correlation length and ion size asymmetry.

Exoelectrogenic behaviors of Shewanella oneidensis MR-1 and cytochrome knock-out mutants on smooth electrodes of different materials

The development of anodes supporting a high rate of current generation stands as a crucial and challenging aspect in microbial electrochemical systems. A well-defined electrode surface morphology is essential for comprehending the impact of material intrinsic properties on microbial current generation, offering molecular insights into the respiration of exoelectrogens with electrodes made of diverse materials. We fabricated smooth electrodes (root mean square roughness below 10 nm) using four materials, each representing a distinct class of materials commonly utilized to construct bioanodes. These electrodes were employed to investigate current generation, electrochemical characteristics, and biofilm formation by Shewanella oneidensis MR-1 and mutants lacking cytochromes MtrC (ΔmtrC), MtrA (ΔmtrA), or CymA (ΔcymA). In reactors inoculated with MR-1, the poly(3,4-ethylenedioxythiophene) polystyrene sulfonate electrodes demonstrated a current density of 12.5 ± 1.1 μA cm-2, surpassing the 3.57 ± 0.50 μA cm-2 observed with indium tin oxide electrodes, while current generation levels by gold and glassy carbon electrodes fell in between. This disparity was not attributed to distinct biofilm formations by MR-1, as it formed stable monolayer biofilms on all types of working electrodes. At least five electron transfer pathways were identified in the MR-1 Vammograms, with the activities of these pathways depending on the electrode materials. The effectiveness of both endogenous and exogenous electron mediators varied with the electrode materials involved. Additionally, a phenazine compound exhibited diverse formal potentials when interacting with the biofilm and different types of electrodes. The mutants displayed varying degrees of impaired current generation and biofilm formation capabilities, with ΔmtrA and ΔcymA being the most affected regardless of the electrode used. However, for a specific mutant, the overall current generation, relative contribution by individual pathways, and biofilm formations underwent significant changes based on the electrode materials employed.

Electrodeposition of NiCo on stainless steel substrate using deep eutectic solvent for efficient hydrogen evolution and methanol oxidation reactions

The electrodeposition of NiCo on a stainless-steel substrate using Deep eutectic solvent (DES) was carried out using constant current methods. A 1:2 mol ratio of ChCl (Choline chloride) and crystalline urea was used to prepare DES. The XRD analysis of the fabricated NiCo@SS showed a highly crystalline nature, and the SEM image revealed the fabricated electrode surface morphology. The composition and oxidation state of the deposited material were confirmed by EDAX and XPS techniques. The prepared electrodes were subjected to LSV and CV studies with 1 M KOH using a three-electrode system to analyse its catalytic ability in the Hydrogen evolution reaction (HER) and methanol oxidation reaction (MOR). Among all the deposited electrocatalysts, NiCo@SS demonstrated the highest catalytic activity and excellent stability for the hydrogen evolution reaction (HER), achieving an overpotential of 257 mV at a current density of 100 mA/cm2. Additionally, NiCo@SS exhibited a remarkable current density of 240 mA at a potential of 0.8 V towards the MOR. The synthesized NiCo@SS possessed excellent low overpotential, low charge transfer resistance, high current density, and large surface area. The explored catalyst of NiCo@SS was examined with different concentrations of methanol using the CV technique. Finally, the stability of NiCo@SS, as examined by chronoamperometry and LSV with 3000 cycles, revealed it to be a robust, stable catalyst towards HER and OER.

Highly transparent and conductive Ga-doped InWO multi-component electrodes for Perovskite photovoltaics

Wide-bandgap Ga-doped InWO (GIWO) transparent conductive electrodes (TCE) were fabricated by co-sputtering IWO and Ga2O3, followed by rapid thermal annealing (RTA), with the effects of the Ga dopant content on the electrical, optical, structural, and morphological properties of the GIWO multi-component electrodes investigated to optimize the GIWO electrode. According to the figure of merit (FOM), the GIWO film with a Ga content of 2.1 at% exhibited a low sheet resistance of 9.9 Ohm/square and high transmittance of 91.71 % at a wavelength of 550 nm. The presence of a high Lewis acid strength (LAS) dopant of Ga (1.16) and W (3.15) led to an increase in the carrier mobility of GIWO and transmittance in the near infrared wavelength region. In addition, the strongly preferred (222) and (400) orientations of the GIWO grains increase the carrier mobility and improve the surface morphology of the GIWO electrodes. The successful operation and superior performance of the planar p-i-n structured perovskite solar cells (PSC) fabricated on GIWO electrodes indicate the feasibility of GIWO as a substitute for conventional Sn-doped In2O3 electrodes. The highest-performing PSC with GIWO electrodes exhibited reliable hysteresis with an efficiency difference of less than 1 % depending on the scan direction under standard AM1.5 G conditions.